Dietary fiber can affect cadmium (Cd) absorption and toxicity, but the effect appears to depend on the type of dietary fiber. The aim of the present study was to compare the effect of dietary sources containing distinct amounts of soluble and insoluble fiber on Cd absorption, accumulation and toxicity in growing rats. The absorption of essential macrominerals (Ca, P and Mg) was also evaluated. Animals received a nutritionally balanced diet with cellulose (cel — control), wheat bran or flaxseed as the fiber source with 0 or 50 mg Cd kg-1 diet, during 30 days. Cd exposure reduced body weight gain, feed efficiency ratio, epididymal fat relative weight and liver relative weight, and increased plasma alanine aminotransferase activity in all fiber groups. The apparent Cd absorption was similar among Cd-groups, but the flax-Cd group had a higher hepatic and renal Cd concentration. Cd decreased the absorption of Ca and P, and increased Mg absorption in the wheat bran and flaxseed groups, but not in the cel group. Although the different fiber sources investigated had no effect on Cd toxicity, the major soluble fiber source, flaxseed, increased Cd retention. Thus, caution should be taken in the intake of flaxseed by Cd-exposed populations.

Strategies to diminish cadmium (Cd) absorption are highly desirable especially where Cd exposure due to environmental contamination is still inevitable. Cd toxicity may be influenced by dietary components, such as fiber and minerals. Multimixtures are low-cost cereal bran supplements used in Brazil and in other countries to counteract malnutrition in low-income populations. This study was aimed at evaluating whether multimixture would reduce Cd effects in young rats. Animals received a diet with or without the multimixture plus 0, 5, or 25 mg Cd/kg (control, Cd-5, and Cd-25 groups) during 30 days. The Cd-5 groups were similar to control groups in all parameters analyzed, except in the higher renal Cd concentration. However, the Cd-25 groups had lower biological growth parameters and renal δ-aminolevulinate dehydratase activity, besides higher renal Cd concentration and plasma alanine aminotransferase activity compared to the controls. The multimixture did not prevent Cd effects in the Cd-25 group, but caused a small reduction in renal Cd concentration in the Cd-5 group. Although this multimixture was ineffective to prevent Cd effects at the higher concentration, it seemed to reduce Cd accumulation at the lower Cd dietary concentration, which is similar to levels of human exposure in some polluted areas.

Multimixtures (MMs) are dietary supplements prepared with low-cost ingredients and food by-products that are widely used in various countries to counteract malnutrition. Although MMs have a high content of minerals, they also contain high levels of dietary fiber and associated compounds, which might bind minerals and impair their absorption. In this study, we investigated the hypothesis that the increased dietary fiber content of MMs would impair gastrointestinal mineral absorption due to the metal-binding capacity of dietary fiber. Thus, the objective of the present study was to feed growing rats with a basal diet, representative of a nutritionally deficient diet, alone or supplemented with a low dietary fiber level MM, intermediate dietary fiber level MM, or high dietary fiber level MM (HF) to evaluate the apparent absorption of calcium, phosphorus, magnesium, manganese, and copper. The relative apparent calcium absorption was slightly decreased by the HF addition, with no change in the absolute apparent absorption. The absolute apparent absorption of phosphorus and magnesium was increased by the intermediate dietary fiber level MM and HF additions, whereas the manganese absorption was increased only by the HF addition. The apparent absorption of copper was not affected by the MM supplementation. The increased apparent absorption of minerals was always related to the increase in the mineral dietary concentration triggered by the MM. Thus, we concluded that the increased dietary fiber levels in the MMs increased the mineral levels, and MMs with intermediate and high fiber levels may be used to improve the mineral balance of poor diets.